US3559644A - Liquid infusion apparatus - Google Patents

Abstract

Liquid infusion apparatus provides reliable administration of liquids and blood transfusions into the body (intravenous, intraarterial or subcutaneous) at a preset and regulated rate in a convenient, inexpensive and completely safe manner. The apparatus includes liquid pumping an valving mechanisms and gas relief means which prevent both the back flow of liquid into the liquid reservoir and the injection of air into the blood stream of the patient.

Description

United States Patent [72] Inventors Paul E. Stolt Menlo Park; Robert F. Shaw, 350 Parnassus, San Francisco, Calif. 941 I 7 [21 Appl. No. 690,440 [22] Filed Dec. 14, 1967 [45] Patented Feb. 2, 1971 [73] Assignee Said Stolt assignor, to said Shaw. by mesne assignment [54] LIQUID INFUSION APPARATUS 4 Claims, 4 Drawing Figs.

[52] US. Cl 128/214, 417/240.417/435; 222/76, 222/203. 222/380; 128/274 [51] Int. Cl A6lm 5/00 [50] Field ot'Search 128/213- [56] References Cited UNITED STATES PATENTS 2,664,085 12/1953 Ryan 128/214 Berkow Med. .lour. & Record July 1925 p. 529

Primary ExaminerDalton L. Truluck Attorney-Albert C. Smith ABSTRACT: Liquid infusion apparatus provides reliable administration of liquids and blood transfusions into the body (intravenous, intraarterial or subcutaneous) at a preset and regulated rate in a convenient, inexpensive and completely safe manner. The apparatus includes liquid pumping and valving mechanisms and gas relief means which prevent both the back flow of liquid into the liquid reservoir and the injection of air into the blood stream of the patient.

PULSER PATENTED FEB 2 I97! SHEET 1 BF 2 I igure 3 INVENTORS PAUL E. STOFT ROBERT F. SHAW ATTORNEY PATENT-Ema 2l97l 3:559:64;

' sum 2 0F 2 TIMER ANDPULSER 38 L5 I F---' 27 i I :g 6

q? isure' 4 v I INVENTORS PAUL E. STOFT ROBERT F. SHAW ATTORNEY LIQUID INFUSION APPARATUS BACKGROUND OF THE INVENTION Conventional infusion apparatus for administering fluids to a patient intravenously, intraarterially, or the like, commonly includes a fluid reservoir, an infusion needle or catheter connected to the reservoir by a drip chamber and a tubing clamp positioned along the length of the plastic tubing. The fluid reservoir is typically elevated well above the patient to provide fluid pressure and the fluid flow rate, observed in the fluid drip chamber as the number of drops per unit time, is set by squeezing the plastic tube a selected amount in the tubing clamp. The disadvantages encountered in conventional infusion apparatus of this type are that the fluid flow rate may decrease and stop due to formation of blood clots in or about the infusion needle, due to variations in resistance to flow through the needle or catheter caused by patient motion or change of bodily position and also due to variation in resistance to flow through the tubing within the tubing clamp caused by the cold flow of the plastic material forming the walls of the tubing within the tubing clamp. These effects tend to vary the flow rate of fluid administered to the patient, thereby requiring frequent inspection and readjustment of the apparatus.

SUMMARY OF THE INVENTION The apparatus of the present invention overcomes these disadvantages by providing liquid-pumping means which provides the required pressure and flow rates independent of variations in the resistance to flow encountered. The liquidpumping means includes apparatus for introducing sufiiciently large pressure pulse in the liquid within a storage chamber to overcome the resistance to flow through an outlet valve and thereby provide the selected liquid infusion pressure and flow rate. The liquid pressure pulses may be generated by a mechanically actuated plunger or may be generated by an electromechanical element which is electrically pulsed to pump the infusion liquid from a storage chamber. In these and other embodiments of the invention, gas relief means are coupled to the storage chamber for preventing the buildup of liquid pressure within the chamber sufficient to produce liquid flow through the outlet valve when the chamber is not filled entirely with the infusion liquid.

DESCRIPTION OF THE DRAWING FIG. I is a side view of the liquid infusion apparatus according to one embodiment of the present invention showing a cross section of the disposable pumping subassembly;

FIGS. 2 and 3 show alternate embodiments of the flotation of valve of FIG. I; and

FIG. 4 is a pictorial view of liquid infusion apparatus according to another embodiment of the present invention which includes an electromechanical pumping element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG; I the liquid infusion apparatus includes a conventional drip chamber 9- connected to receive the infusion liquid fromreservoir 11. Liquid from the drip chamber 9 is supplied to thestorage chamber 13 of the pumping means 15 through theinlet valve 17 which includes a ball or other valve element that floats into closed position in the infusion liquid within thechamber 13.

Apump cylinder 19 with aslidable piston 21 therewithin is connected to receive the liquid in thechamber 13 and anoutlet valve 23 is coupled to thechamber 13 to control the outflow of liquid from the chamber. A suitable length offlexible tubing 25 connects the outlet end ofchamber 13 to the infusion needle orcatheter 27. Actuating means 29 for thepiston 21 may include a spring motor orelectric motor 31 coupled to thepiston 21 through a connectingrod 32 which is pivotally attached to thecrank arm 33 on the rotatable shaft of themotor 31 at a selected distance from the shaft. Of course, the

actuating means may also include other suitable prime movers such as electrical solenoids or the like for reciprocatingly actuating thepiston 21 within thecylinder 19.

In operation, the actuating means 29 moves thepiston 21 within thecylinder 19 in a direction away from thechamber 13 to draw fluid from thechamber 13 into the cylinder I9. This causes fluid to be drawn from the drip chamber 9 past the inlet valve I7 into thechamber 13 and cylinder I9 while theoutlet valve 23 remains closed. When thepiston 21 is moved toward the chamber I3 by the actuating means 29, the increase in liquid pressure produced thereby aids in closing theinlet valve 17 and opens theoutlet valve 23 when the liquid pressure inchamber 13 overcomes the slight bias against outflow through theoutlet valve 23 produced by thespring 24. This spring bias against outflow through theoutlet valve 23 assures that liquid does not flow to the needle under the pressure head provided by the elevation of the reservoir above the outlet valve. A selected amount of liquid thus flows past theoutlet valve 23 and through thetubing 25 to theneedle 27 only upon the return stroke ofpiston 21. For acylinder 19 of given internal diameter, the amount of liquid supplied to theneedle 27 may thus be regulated by altering the stroke of the piston, for example, by altering the position alongcrank arm 33 of the connectingrod 32 coupling to the crank arm or by altering the rotational speed of themotor 31.

Theinlet valve 17 is selected to displace on amount of the infusion liquid which weighs more than thevalve element 17 so that the element is urged into the closed position by the buoyant force thus produced. Thus, if air is drawn into thechamber 13 and the liquid level drops, for example, when thereservoir 11 and drip chamber 9 are empty, thefloating element 17 is no longer urged into closed position and thereby provides a gas relief opening back to the reservoir and drip chamber for air within thechamber 13. The return stroke ofpiston 21 thus is unable to create sufficient liquid pressure inchamber 13 to overcome the bias against outflow provided byoutlet valve 23 and thus no air can be administered to the patient. Other embodiments of floating inlet valve means according to the present invention are shown in FIGS. 2 and 3. In these embodiments, thefloating element 18 may actuate anonfloating valve 20 or may be thevalve element 18 which forms the sealing engagement with the upper walls of the chamber. In each of these embodiments, when the liquid level in thechamber 13 drops due to air being drawn into the chamber, the floating inlet valve is no longer buoyed into closed position and the air within the chamber is thus vented back toward thereservoir 11 so that liquid pressure cannot build up within thechamber 13 to overcome the bias against liquid outflow throughoutlet valve 23.

Referring now to FIG. 4, there is shown another embodiment of the present infusion apparatus in which the liquid pressure to overcome the bias against outflow of liquid through outlet valve means 35 is provided by a mechanical orelectromechanical element 37. Thiselement 37 is disposed on thetop 38 of a conical ornozzlelike chamber 39 remote from the outlet means 35 positioned at the apex 41 of theconical chamber 39 for mechanically displacing thetop 38 in response to an applied electrical signal. Theelement 37 may thus be a solenoid having a movable armature coupled to thesurface 38 or, preferably, may be a piezoelectric element. A fluidconduit including tube 43 and drip chamber 9 connects the reservoir 1 l to the internal region of theconical chamber 39 through anaperture 36 in thetop surface 38 of thechamber 39. Theelement 37 may have a toroidal shape to facilitate symmetrical location of theinlet aperture 36 andfluid conduit 43 substantially at the center of thetop surface 38.Suitable excitation signals 45 are applied to theelement 37 by the timer andpulser 47. Thetop surface 38 of theconical chamber 39 is flexible in the direction along the central axis of the conical symmetry of thechamber 39 to enable the mechanical displacement produced by theelement 37 to establish a pressure pulse in the liquid within thechamber 39. The mounting bracket .49 which supports thechamber 39 also supports theelement 37 in engagement with thetop surface 38 so that longitudinal extension of theelement 37 in response to excitation signal applied thereto from timer andpulser 47 are coupled to the fluid within thechamber 39 through the diaphragmlike or plungerlike movement oftop surface 38. Theconduit 43, drip chamber 9.chamber 39. outlet valve 35 and thetubing 25 andneedle 27 may all be conveniently disposable and replaceable with similar prestcrilized replacement parts.

In operation. theelement 37 displaces thetop surface 38 upward in response to an excitation signal of sufficient amplitude and proper polarity applied to theelement 37 by the timer andpulser 47. This upward movement of thetop surface 38 with respect to thechamber 39 increases the internal volume of thechamber 39. The drop in internal pressure produced thereby causes liquid to be drawn through theaperture 36 in thetop surface 38 from thechamber 39. OUtlet valve 35 remains closed so no liquid is administered to the patient during this phase of operation. When the polarity of the drive signal applied to theelement 37 from timer andpulser 47 reverses, thetop surface 38 is suddenly driven downward. This causes a pressure wavefront to propagate through the liquid inchamber 39 in a focused or converging direction predominantly toward the outlet valve 35 at the apex end ofchamber 39. This pressure wave momentarily overcomes the bias against outflow through valve 35 and expels a small amount of liquid into thetube 25 and out throughneedle 27. If this pressure wavefront is suitably focused there will be no expulsion of liquid from thechamber 39 back toward the drip chamber 9 through thesmall aperture 36.

If, however, focusing of this pressure wavefront is inadequate to assure unidirectional propagation of the pressure pulse, then a small amount of liquid may be expelled from thechamber 39 back toward the drip chamber 9 through thesmall aperture 36. However, since theelement 37 may produce short pulses and since theaperture 36 may be very small in diameter, such backflow is negligibly small and produces no deleterious effects. Thus, the flow rate of infusion liquid into a patient may thus be regulated by setting the pulse amplitude and repetition rate ofsignals 45 applied to theelement 37 by the timer andpulser 47. Thislatter element 47 may include a conventional multivibrator circuit arranged to operate from apower source 46 to provide the necessary driving signals 45 at variable pulse amplitude and repetition rate.

The embodiment of FIG. 4 also includes gas relief means which prevents infusion of air when thereservoir 11 is empty. If liquid is expelled fromchamber 39 to an extent that air is present in the chamber, then the compressibility of the air and the gas relief opening ataperture 36 which presents negligible resistance to gas flow prevent the movement ofelement 37 andsurface 38 from establishing asufficient pressure wave 42 within the remaining liquid in thechamber 39 to overcome the bias against outflow through valve 35.

Therefore, the apparatus of the present invention may be left unattended without risk of administering air into a patient when the reservoir is empty and without risk of the liquid infusion rate changing due to such factors as the formation of blood clots about the needle. Also, if blood clots tend to develop about the needle tending to block the infusion of liquid, the liquid pressure within the tubing and needle builds up with each pumping phase until the blockage is cleared by the liquid under pressure.

We claim:

1. Liquid infusion apparatus for use with source means containing a liquid to be administered to a patient, the apparatus comprising:

a chamber for confining a volume of fluid;

compressor means coupled to said chamber and having a movable boundary wall disposed to communicate with fluid within said chamber for changing the volume of fluid within said chamber at a selected rate in response to movement of said boundary wall;

outlet valve means coupled to said chamber for providing outlet flow of fluid therethrough only for values of fluid pressure exerted thereon above a selected value of bias pressure;

conduit means coupled to said outlet valve means for supplying the outlet flow of fluid to a patient; and

fluid inlet means connecting said source means with said chamber, said fluid inlet means consisting only of an aperture in the upper portion of said chamber for permitting bilateral flow of fluid therethrough between said source means and said chamber in response to movement of said secondary wall. the size of said aperture introduces less resistance to flow therethrough of gas than of liquid:

a. the selected change of volume of fluid within said chamber in response to movement of said boundary wall with said chamber filled with liquid exceeds the back flow of liquid through said aperture for producing a buildup of pressure within said chamber to overcome said selected value of bias pressure of said outlet valve and permit outlet flow of liquid through said conduit means to a patient, and

b. the selected change of volume of fluid within said chamber in response to movement of said boundary wall with gas enclosed in the upper portion of said chamber in the region of said aperture is less than the backflow of the gas through said aperture for preventing buildup of pressure within said chamber adequate to overcome said selected value of bias pressure of said outlet valve.

2. Liquid infusion apparatus for use with source means containing a liquid to be administered to a patient, the apparatus comprising:

a chamber for confining a volume of fluid and including converging walls forming an internal region of decreasing cross-sectional area with length of the chamber for focusing a pressure wave at an outlet disposed near the end of said chamber of smallest cross-sectional area;

outlet valve means disposed at said outlet and coupled to said chamber for providing outlet flow of liquid therethrough only for values of pressure exerted thereon above a selected value;

fluid inlet means connected for receiving liquid from the source means and coupled to said chamber for supplying fluid therethrough to said chamber;

transducer means disposed with respect to said chamber near the end thereof of largest cross-sectional area for increasing the fluid pressure in the internal region of said chamber to a value above said selected value for producing outflow of liquid through said outlet valve means in response to an electrical signal applied to said transducer means;

gas relief means including an aperture of selected cross section disposed at the fluid inlet in a wall of said chamber near the end thereof of largest cross-sectional area; and

conduit means coupled to said outlet valve means for supplying the outlet flow of liquid to a patient.

3. Liquid infusion apparatus as in claim 2 wherein:

said transducer means is a piezoelectric element arranged on a wall of said chamber disposed near the end thereof of largest cross section to displace a portion of said wall in response to electrical signal applied to said element for producing a pressure increase in the infusion liquid within said chamber near the end thereof of smallest cross section in excess of said selected value.

4. Liquid infusion apparatus as in claim 3 wherein:

said chamber is conieally shaped;

said transducer means includes a toroidally shaped piezoelectric element disposed on the upper wall of said chamber remote from said outlet valve for producing a pressure wave in infusion liquid within said chamber in response to electrical signal applied to said piezoelectric element, whereby the pressure wave is confined and focused by the conieally shaped chamber to exert liquid pressure on said outlet valve in excess of said selected value; and

said aperture is disposed in said upper wall of said chamber within the inner area of said toroidally shaped piezoelectric element.

Claims (3)

1. 2. Liquid infusion apparatus for use with source means containing a liquid to be administered to a patient, the apparatus comprising: a chamber for confining a volume of fluid and including converging walls forming an internal region of decreasing cross-sectional area with length of the chamber for focusing a pressure wave at an outlet disposed near the end of said chamber of smallest cross-sectional area; outlet valve means disposed at said outlet and coupled to said chamber for providing outlet flow of liquid therethrough only for values of pressure exerted thereon above a selected value; fluid inlet means connected for receiving liquid from the source means and coupled to said chamber for supplying fluid therethrough to said chamber; transducer means disposed with respect to said chamber near the end thereof of largest cross-sectional area for increasing the fluid pressure in the internal region of said chamber to a value above said selected value for producing outFlow of liquid through said outlet valve means in response to an electrical signal applied to said transducer means; gas relief means including an aperture of selected cross section disposed at the fluid inlet in a wall of said chamber near the end thereof of largest cross-sectional area; and conduit means coupled to said outlet valve means for supplying the outlet flow of liquid to a patient.
2. 3. Liquid infusion apparatus as in claim 2 wherein: said transducer means is a piezoelectric element arranged on a wall of said chamber disposed near the end thereof of largest cross section to displace a portion of said wall in response to electrical signal applied to said element for producing a pressure increase in the infusion liquid within said chamber near the end thereof of smallest cross section in excess of said selected value.
3. 4. Liquid infusion apparatus as in claim 3 wherein: said chamber is conically shaped; said transducer means includes a toroidally shaped piezoelectric element disposed on the upper wall of said chamber remote from said outlet valve for producing a pressure wave in infusion liquid within said chamber in response to electrical signal applied to said piezoelectric element, whereby the pressure wave is confined and focused by the conically shaped chamber to exert liquid pressure on said outlet valve in excess of said selected value; and said aperture is disposed in said upper wall of said chamber within the inner area of said toroidally shaped piezoelectric element.

Images